1 files changed, 71 insertions, 0 deletions
diff --git a/bzipper_macros/src/discriminant_iter/mod.rs b/bzipper_macros/src/discriminant_iter/mod.rs
new file mode 100644
index 0000000..ea34f6d
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+++ b/bzipper_macros/src/discriminant_iter/mod.rs
@@ -0,0 +1,71 @@
+// Copyright 2024 Gabriel Bjørnager Jensen.
+//
+// This file is part of bZipper.
+//
+// bZipper is free software: you can redistribute
+// it and/or modify it under the terms of the GNU
+// Lesser General Public License as published by
+// the Free Software Foundation, either version 3
+// of the License, or (at your option) any later
+// version.
+//
+// bZipper is distributed in the hope that it will
+// be useful, but WITHOUT ANY WARRANTY; without
+// even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Less-
+// er General Public License along with bZipper. If
+// not, see <https://www.gnu.org/licenses/>.
+
+use crate::Discriminant;
+
+use std::borrow::Borrow;
+use syn::Variant;
+
+pub struct DiscriminantIter<I: IntoIterator<Item: Borrow<Variant>>> {
+	variants: I::IntoIter,
+	prev:     Option<Discriminant>,
+}
+
+impl<I: IntoIterator<Item: Borrow<Variant>>> DiscriminantIter<I> {
+	#[inline(always)]
+	#[must_use]
+	pub fn new(variants: I) -> Self {
+		Self {
+			variants: variants.into_iter(),
+			prev: None,
+		}
+	}
+}
+
+impl<I: IntoIterator<Item: Borrow<Variant>>> Iterator for DiscriminantIter<I> {
+	type Item = (Discriminant, I::Item);
+
+	#[inline]
+	fn next(&mut self) -> Option<Self::Item> {
+		let variant = self.variants.next()?;
+
+		let discriminant = if let Some((_, ref discriminant)) = variant.borrow().discriminant {
+			Discriminant::parse(discriminant)
+		} else if let Some(discriminant) = self.prev {
+			let value = discriminant.0
+				.checked_add(0x1)
+				.unwrap_or_else(|| panic!("overflow following discriminant `{discriminant:?}`"));
+
+			Discriminant(value)
+		} else {
+			Default::default()
+		};
+
+		self.prev = Some(discriminant);
+
+		Some((discriminant, variant))
+	}
+
+	#[inline(always)]
+	fn size_hint(&self) -> (usize, Option<usize>) {
+		self.variants.size_hint()
+	}
+}